During his military service in the Mexican-American War, he was wounded at the Battles of Monterrey and Buena Vista. He was awarded a congressional award and a sword from the State of New Jersey. He rose to the rank of Captain, but resigned his commission in May 1856 to become a planter in Mississippi.

Photo of French from his book.

When the Civil War began, French sided with the South. On February 12, 1861, French was appointed chief of ordnance of the state of Mississippi; and on October 23, 1861, he was appointed a brigadier general in the provisional army of the Confederate States of America. French became a major general on August 31, 1862. General French commanded a brigade and subsequently a division under Gen. Daniel Harvey Hill at Petersburg, Virginia. He led a demonstration against Harrison's Landing on July 4, 1862 and one against Suffolk, Virginia on September 22, 1862. (Fort French at Suffolk was nanmed for him.) In 1863, French led a division under LTG James Longstreet in the Siege of Suffolk. French's division intervened in the Battle of Suffolk (Hill's Point), with its commander waiting for the federals who had seized Fort French to withdraw from their exposed position.

After the war, he returned to his work as a southern planter, and later authored the book "Two Wars" about his war experiences. French had married Mary Fontaine Abercrombie on 12 January 1865. Mary Fontaine Abercrombie died on 16 May 1900 at Atlanta, Georgia. They had two sons and a daughter. Gen French died in Pensacola, Florida in 1910. Gen French was buried in Florida but a memorial to him was constructed in the Laurel Hill Cemetery in Philadelphia, Pennsylvania.[2] There is also a bust and marker of French in the National Military Park in Vicksburg, Mississippi. [2]

^Armstrong, Samuel S. "Trenton in the Mexican, Civil, and Spanish-American Wars", accessed May 9, 2007. "Samuel Gibbs French was a native of Salem County,N.J. and graduated from West Point in 1843 with the brevet rank of Second Lieutenant and assigned to the Third U.S. Artillery, July 1, 1843."